Catalytic Upgrading Of Pyrolysis Oil And Gas From Low-rank Coals

Coal pyrolysis was an effect way to meet the demand of energy and chemicals for the oil-poor but coal-rich countries.However,high content of heavy components(boiling point over 360 ?)in tar would cause unstable operation of the whole system,resulting in the failure of industrialization of coal pyrolysis process.The key to solve these problems is to decrease the content of heavy component in tar through catalytic upgrading using catalysts with low-cost,simple preparation process,high-efficiency,and high-reserves during coal pyrolysis process.This study proposed the integrated process coupling comprehensive utilization of solid waste red mud(RM),harmless disposal of waste sulfuric acid from alkylation process,and catalytic upgrading of coal pyrolysis volatiles.Aiming at catalytic upgrading coal pyrolysis volatiles via in-situ and ex-situ catalytic process using red mud-based catalyst and surface functionalized carbon-based catalyst,this study investigated the property changes of red mud during acid-alkali treatment,the self-assembly process of alkylation waste sulfuric acid,and the high value utilization of byproduct from red mud acidization process.In the fixed-bed or two-stage fixed-bed reactor,different kinds of catalysts were investigated to improve tar quality during catalytic coal pyrolysis.This study will contribute to coal pyrolysis reaction control and resource utilization of solid and liquid wastes by providing feasible methods and theoretical support.1.In-situ catalytic coal pyrolysis over red mud-based catalyst.Red mud-based catalyst(RMC)with different sodium content were prepared by using acid-alkali treatment.It was found that changing sodium content could modify the characteristics of RMC.Moreover,the effects of composition and structure of catalyst on catalytic upgrading performance of RMC was investigated in a fixed-bed reactor by mix shaping of coal and RMC with different sodium contents.After adding 4wt.%RMC with sodium content of 3.2 wt.%into coal,the yield of light tar(boiling point<360?)increased to 7.7 wt.%and the light fraction in tar was as high as 74.0%,which were much higher than those from coal pyrolysis without catalyst.The content of sodium in the RMC had a great influence on product distribution of coal catalytic pyrolysis.The low-content sodium with high concentration acids contributed to the formation of coke.Whereas,with the increase of sodium content in RMC,coking was suppressed but more gaseous products were produced.The iron oxide in RMC was reduced via providing lattice oxygen during catalytic coal pyrolysis,thus prompting C-C bond cleavage and yield of CO2 and CO.The titanium species in RMC improved the light tar fraction.The acid-alkali treatment could prepare the RMC with desired ability for catalytic coal pyrolysis via composition and structure modification of raw red mud.2.Ex-situ catalytic coal pyrolysis over red mud-based catalyst.RMC was used as catalyst for upgrading coal pyrolysis volatiles in a two-stage fixed-bed reactor.The results showed that the yield and fraction of light tar after catalytic upgrading using nitric acid and alkali treated RMC(NC)with sodium content of 4.9 wt.%(10 wt.%of the tested coal)at 500 ? were 7.4 wt.%and 80.0%,respectively,which increased by 12.1%and 33.3%in comparison with that from coal pyrolysis without catalyst.Moreover,the SCWN with low-content of sodium(0.4-1.3 wt.%)was prepared by further water washing after sulfuric acid and alkali treatment.The best catalytic performance of these catalysts was 7.0 wt.%and 80.0%of light tar yield and fraction at 500 ? over 10 wt.%SCWM with sodium content of 1.1 wt.%of tested coal.The characterization of the RMC showed that further water washing lowered the sodium content but elevated the specific surface area of RMC,resulting in more catalytic cracking reaction,coke formation,and lower tar yield.3.Ex-situ catalytic coal pyrolysis over sulfated carbon-based catalysts,red oil-derived carbon materials(RDCMs).Surface functionalized carbon-based catalysts,RDCMs were prepared by the self-assembly process from waste red oil(RO)produced in industrial alkylation process.The characterization results showed that the alkene in the RO formed the carbon-based materials with doped sulfur and high specific surface area through reactions of addition,cyclization,aromatization,et al.The performance of carbon-based catalysts on upgrading of coal pyrolysis volatiles was investigated in a two-stage fixed-bed reactor.Compared with acti'vated carbon(AC)or char,RDCMs exhibited better performance in increasing the yield and fraction of light tar.The higher specific surface areas and relatively more defects of RDCMs promoted the conversion of more heavy tar into light tar.The high-content doped sulfur in RDCMs contributed to more oxidation reaction in the secondary reaction for producing gaseous products.The pyrolysis water could be activated on the sulfur functional group to form ·H and OH radicals,which were able to stabilize the larger radical fragments from cracking of larger molecular in tar forming more oxygenated organic compounds.The light tar yield and fraction of catalytic upgrading over RDCMs(10 wt.%of the tested coal)at 500 ? were 7.9 wt.%and 80.0%,respectively,which increased by 19.6%and 33.3%in comparison with that from coal pyrolysis without catalyst.4.Ex-situ catalytic coal pyrolysis over red mud modified char(RMMC)and in-situ catalytic coal pyrolysis using discard solution from red mud acidification process.In order to solve the problems of recovery of RMMC after in-situ catalytic coal pyrolysis and high demand of metal solution for in-situ catalytic coal pyrolysis,the RMMC and discard solution from red mud acidification process were used to ex-situ and in-situ catalytic coal pyrolysis,respectively.The light tar yield and fraction of catalytic upgrading over RMMC(10 wt.%of the tested coal)at 450 ? were 6.9 wt.%and 77.0%,which increased by 4.5%and 28.3%,respectively,in comparison with that from coal pyrolysis without catalyst.Compared with that of char,the specific surface area,metal content of RMMC increased dramatically,resulting in better ability of catalytic heavy component cracking.After adding 0.25 wt.%discard solution containing iron and aluminum species into coal,the light tar yield and fraction were 7.7 wt.%and 74.0%,which increased by 15.2%and 21.7%,respectively,in comparison with that from coal pyrolysis without catalyst.The metal component in the discard solution could promote the catalytic oxidation reaction and cracking reaction,thus elevating the light tar yield and fraction.5.Ex-situ catalytic coal pyrolysis over HZSM-5 with different SiO2/Al2O3 ratios.The effect of SiO2/Al2O3 ratio of HZSM-5 on the tar quality and coke formation during catalytic coal pyrolysis was investigated.The results showed that the carbon deposition amount reached to 120.1 mg/g-catalyst over H23.Moreover,the carbon deposition decreased with the increase of the SiO2/Al2O3 ratio.The tar quality was related with the ratio of strong and weak acid amount.The higher ratio benefited light tar fraction.Additionally,with the increase of SiO2/Al2o3 ratio,the aromatics content in the tars decreased,indicating the stronger acid sites promoted oligomerization,cyclization,dehydrogenation reaction of olefins,thus causing higher yield of aromatics during catalytic coal pyrolysis.